A light emitting diode (LED) may constitute a light emitting source using a compound semiconductor material such as GaAs-based, AlGaAs-based, GaN-based, InGaN-based, and InGaAlP-based semiconductor materials.
Such a LED is packaged and used as a light emitting device which emits light of various colors. The light emitting device is used as a light source in various fields, such as a lighting indicator for displaying a color, a character indicator, and an image indicator.
Particularly, in case of an ultraviolet LED (UV LED), a short wavelength may be used for sterilization and purification, and a long wavelength may be used for an exposure apparatus or a curing apparatus. Since a luminous intensity of a light emitting device having such a UV LED is low, it is required to improve the luminous intensity.